Greg5OH

sounds like a bushing or contact/ rub condition to me. Already did uca bushings with oem lemforderz.
what is strange is that I cannot replicate the sound if I put it on the four post or a two post hoist and use a jack to manually raise the suspension .
it only seems to happen under the jarring type of bp such a speedbump .
also went through with the prybar and tried moving all of the individual control arms separatelu.

https://youtu.be/q27rIr0LerE

target39

You mentioned checking each individual control arm, as well as recently replacing their bushings, so I'm going to assume it's not those. At this point, it could be the sway bar bushings or the sway bar connecting links. Another possibility is the subframe bushings. Perhaps they were touched for alignment after replacing the control arm bushings. Highly unlikely, but a possible factor nonetheless. I've heard that noise before and replacing the sway bar connecting linkages eliminated that noise. They're relatively cheap and their rubber bushings go bad frequently, so I would replace those anyway even if they still looked good.

mishar

Most likely it's sway bar bushings. Unfortunately they come fused to the sway bar and has to be replaced with it. Fortunately not too expensive and easy to replace.

Shark_V8

I have the same thing and my son 's car - well the bushings broke the suspension arm. I was just at the dealer ordering new bushes $35 ea.

There has to be a way to lube these suckers Jager-style, assuming they are still intact. I'm thinnking about it cause it's a pain to re/re these things.

For example, surgically drill a port into the bushing space, then inject my fave lube LPS#2, let it soak out, BYU.

MP4.2+6.0

Control arm bushing failure is not lube related in any way. The suspension has to move in all three dimensions so it is just that rubber area that takes all the various torsional forces. A way too lightweight design from late 90's A4 era with nothing like the weight, torque, braking forces and unsprung weight of the way heavy larger wheels and brakes even of the D3. My last D3 change went to S8 bushings (arms). When it gets to 150-175K have to see if the goes any better.

Playing out now same way on D4 now BTW as miles creep up. Here is a D4 post literally from this afternoon (at reply 10) confirming it remains sort of an oddball periodic maintenance fix: https://www.audiworld.com/forums/a8-...stion-2911094/

dvs_dave

I wonder if Audi have deliberately engineered this as a sacrificial part to save more expensive parts having to take the beating. It can't be an engineering oversight after 2 decades of the same.

target39

They are certainly aware that the control arm bushings are relatively undersized for this type of application (large saloon car) as it's fairly common knowledge that they fail quite prematurely relative to their smaller sedans'. As long as it can endure 100,000mi/160,000km, it won't be their priority to redesign the suspension geometry and components for better durability, especially if it means increasing weight and costs.

You also have to take into account that not only do these larger cars have more weight on those bushings, they have adaptive air suspensions that dynamically change the height of each air spring. Rubber bushings are designed to be tightened at a specified ride height position and to provide torsional resistance (twist) to return to its resting position like a spring. When you have an air spring that can range from -1in/25mm to +1in/25mm from normal ride height, there is a constant torque applied to the rubber bushing when not at normal ride height, adding stress, which could accelerate wear. If you want your bushings to last longer, leave the car at normal ride heights, especially when sitting, unless absolutely necessary. Temperature cycles also play a role, but that issue is present in all cars.

As to whether or not Audi engineered it to fail early deliberately to save wear on other parts, I don't doubt it. If the control arm and sway bar bushings outlived other suspension parts, the weakest links in the front suspension aside from the air spring would then become the ball joints. You don't want your ball joints to fail before your bushings. Bushings fail earlier = bad noise/ride; ball joints fail earlier = loose spindle = not good.

Shark_V8

TT = Complete Control arm failure

mishar

Guys, you are trying to justify obvious design flow. Little bit bigger bushings would last forever. Just like the lower ones. No need for a weak spot to save anything. For a month I was driving borrowed 2005 Civic. Not a sound from suspension. Shame on you Audi. Period.

Shark_V8

I got 4x rubber bushings from Audi today for the TT, rear not the A8. And I'm wondering why are these a problem? How do they work? and why do bushings squeak?

Rubber donut style bonded bushings are pretty cool that they flexably join two metal parts and allow a certain range of motion, without moving, only flexing. In the TT's case, rubber has a finite service life, just like tires etc. Starts to harden and the ROM is severly reduced. This stress causes the control arm fork failure

But squeaking is another story. Squeaks are caused by movement (not flex), and slip in the joint. I have not looked at the A8's suspension yet but I dobut there is anything in there designed to slip (if so lube it?). If it's not designed to slip and now is, the bond between the parts is lost and must be replaced.

Sway bar bushings are a clamp/compressed support design. The bar itself doesn't travel much, I'm thinking the bushing should grab and flex with the bar. If the bushing is too hard, it will no longer flex and therefore squeak.

In the case of our Reflex Beetle this is the last pce in our suspension puzzle. Everything has been done! The bushings are worn to the point there is metal-metal and some serious rattling. New bushes were cheap, just have to install them.